1. Field of the Invention
The present invention relates generally to a mobile communication system, and more particularly to an apparatus and a method for determining a location of a user equipment (UE).
2. Description of the Related Art
Recently, the wide spread use of UEs has expanded throughout the world. Further, in a global mobile communication system, many users want to receive application services (e.g., traffic, daily information, etc.) using location information of UEs equipments. Accordingly, user location information acquisition systems using UEs have been commercialized in some countries and mobile communication network areas (e.g., SK telecom and KTF in Korean mobile communication network area, and NTT, DoCoMo, Sprint PCS, KDDI, Vodafone in Japan and Western mobile communication network areas).
In order to provide application services using location information, it is necessary to determine a location of a UE in advance. That is, the application services using location information are created on the basis of geographical position information of a UE, which is determined from the location of the UE.
In order to acquire the geographical position information of a UE, the UE must receive a positioning service, regardless of the location of the UE. That is, the UE must receive the positioning service, regardless of whether the UE is located in a home area or a roaming area.
The positioning service is provided by a location platform (LP) contained in a network. For example, a home location platform (HLP) contained in a home network or a visiting location platform (VLP) contained in a roaming network provides auxiliary location information (e.g., auxiliary GPS information) to the UE or performs a location calculation using information received from the UE, in order to provide the positioning service.
The location of a UE in the mobile communication network can be determined by various ways, including three representative examples, which will be described below.
First, the location of a UE can be determined for each cell by using information of the cell nearest to the location of the UE or by using information of the cell managing the UE.
Second, the location of a UE can be determined based on the network. In this network-based positioning, intensity of transmission and reception signals between a node B (or base station), a UE a time-of-arrival (TOA) of a radio wave signal transmitted from the node B to the UE, or a time-difference-of-arrival (TDOA) of a radio wave signal between the UE each of multiple node Bs is calculated. Thereafter, triangulation is performed using the TOA or TDOA, in order to determine the location of the UE.
Third, the location of a UE can be determined by using a global positioning system (GPS) developed by the U.S. Department of Defense.
From among the above-described positioning schemes, the positioning scheme using the GPS is employed in the mobile communication network together with supplementation of the GPS technique. Such a positioning scheme using a supplemented GPS is called a network assisted GPS (NA-GPS). The NA-GPS transmits auxiliary GPS information, which is necessary to determine the location of a UE using a network (particularly, using the mobile communication network), to the UE, thereby shortening the time-to-first-fix (TTFF) of the UE.
The auxiliary GPS information transmitted to the UE in a network includes satellite IDs of the respective satellites, almanac data, satellite orbit information, a clock error correction value, an ionosphere correction value, a differential GPS (DGPS) correction value, and a list of invisible satellites. The almanac data is location information (e.g., a model) of a satellite according to time sections for a predetermined time period, which is used to detect an approximate location of the satellite, particularly to distinguish a visible satellite. The satellite orbit information and the clock error correction value are information for providing an accurate model of a satellite location to a UE. The ionosphere correction value is used to correct an ionosphere delay error, which occurs when a radio signal passes through an ionosphere contained in a pseudo distance between a satellite and a UE, by about 50%. The ionosphere correction value changes slower than other information.
The DGPS correction value improves the accuracy of a UE location, by enabling a basic node B to calculate and remove a deviation error contained in the pseudo distance. The almanac data, the satellite orbit information, the clock error correction value, and the DGPS correction value must be determined according to satellites.
FIG. 1 is a block diagram schematically illustrating a conventional mobile communication system. More specifically, FIG. 1 illustrates a mobile location service (MLS) system for determining the location of a UE in a mobile communication network. The mobile communication system for determining the location of a UE includes a UE 110, a node B (or base station) 120, a radio network controller (RNC) 130, a home location platform (HLP) 140, a core network (CN) 150 and a mobile location service client (MLS client) 160.
The node B 120 transmits a radio wave signal to the UE 110 located in a specific cell. Also, the node B 120 measures a radio wave signal received from the UE 110, and transmits predetermined data (e.g., TODA) required to determine the location of the UE 110 to the RNC 130. In this case, a Uu interface is used for communication between the node B 120 and the UE 110.
The RNC 130 manages the radio resources of the node B 120, controls a procedure for determining the location of the UE 110, and performs location calculation. In this case, an Iub interface is used for communication between the RNC 130 and the node B 120.
The HLP 140, which is also called a location platform (or location server), provides auxiliary location information to the UE 110, and performs a location information service by performing location calculation and the like. For example, the HLP 140 transmits the auxiliary GPS information to the UE 110, which is one of the auxiliary location information, thereby enabling a network-assisted GPS service to be provided to UEs 110 located in a relevant network.
The CN 150 manages information about the UEs 110 and performs mobility management, session management, and call management. Accordingly, the CN 150 and the RNC 130 communicate with each other using an Iu interface.
The MLS client 160 is connected to the network and provides a service in relation to locations of the UEs 110. That is, the MLS client 160 requests location information of a specific UE 110 from the CN 150 and provides a location service to the relevant UE 110 using the location information. In this case, the MLS client 160 and the CN 150 communicate with each other using an Le interface.
In the above-described system of FIG. 1, when the UE 110 is located in a home network, the UE 110 receives auxiliary location information (e.g., auxiliary GPS information) from the HLP 140 contained in the home network. The HLP 140 may calculate the location of the UE 110, i.e., the location of the UE 110 is determined by the HLP 140.
Referring to FIG. 2, when the UE 110 roams from a home network 100 to another network 200, i.e., when the UE 110 visits another network 200, the UE 110 may determine the location of the UE 110, by using either a visiting location platform (VLP) 240 contained in the network 200 (in which the UE 110 is roaming) or the HLP 140 contained in the home network 100.
However, in order to determine the location of a roaming UE 110 using the VLP 240, the VLP 240 must be able to have a positioning capability, such as information about whether or not various positioning schemes according to required location accuracy are supported and information about whether or not an assisted GPS (A-GPS) scheme in a control plane and a user plane is supported, according to a request of the UE 110, and personal location information of the UE 110 must be kept secret. Therefore, when the roaming UE 110 requests auxiliary location information for determining a location in a user-plane A-GPS scheme, the positioning scheme using the VLP 240 may cause a number of problems. That is, if the VLP 240 supports only a control-plane A-GPS scheme, the VLP 240 cannot provide auxiliary GPS information to the UE 110. Further, there is another problem in that the personal location information of the UE 110 is disclosed as soon as the positioning service begins between the VLP 240 and the UE 110.
In order to determine the location of a roaming UE 110 using the HLP 140, a regional range where the HLP 140 can provide auxiliary location information (e.g., auxiliary GPS information) must include a visiting area where the UE 110 is located.
In addition, although the positioning scheme using the HLP 140 has a superior capability in security and protection of personal location information, the positioning scheme using the HLP 140 has a disadvantage in that the accuracy of auxiliary location information (or auxiliary GPS information) is poor, as compared with the case of using the VLP 240. Therefore, in order to improve the quality of the positioning service, it is preferred that the UE 110 selects a location platform in consideration of both the positioning capability of the HLP 140 or the VLP 240, and capability factors requested by the UE 110, e.g., location accuracy, protection of personal location information, security, etc.
However, until now, there has been no such a method capable of permitting a roaming UE 110 to select a location platform in consideration of the above-described positioning capability and capability factors requested by the UE 110, in order to determine the location of the UE 110.